I've never had that issue with Grok. Latest studies I've seen put him in a very neutral zone. Left/Center/Right politics were all about the same percentages in his replies. Gemini was similar. Other two were heavily left wing leaning. When it comes to politics and world events, I find Grok to be neutral and it will push back. It helps that he is fetching it directly from X and shows references. Others just Google for biased news articles to present their idea.
I don’t find Opus to be overly left-leaning. I think it’s generally pretty balanced with a slight lean left, but when pressed it will happily steelman rightwing arguments and operate within a right-leaning belief framework in good faith. (I found OpenAI’s models much less willing to do that, but it’s been a while since I tried, I should retest.)